Mobile communication systems were developed to provide the subscribers with voice communication services on the move. With the rapid advance of technologies, the mobile communication systems have evolved to support high speed data communication services beyond the early voice-oriented services. However, the limited resource and user requirements for higher speed services in the current mobile communication system spur the evolution to more advanced mobile communication systems.
As one of the next-generation mobile communication systems to meet such requirements, standardization for a Long Term Evolution (LTE) is underway in the 3rd Generation Partnership Project (3GPP). LTE is a technology designed to provide high speed packet-based communication of up to 100 Mbps. In order to accomplish this aim, a discussion is being held on several schemes such as reducing the number of nodes located in a communication path by simplifying a configuration of the network and approximating wireless protocols maximally to wireless channels.
FIG. 1 is a diagram illustrating normal LTE mobile communication system architecture.
As shown in FIG. 1, the radio access network of the LTE mobile communication system includes a next generation base station (hereinafter, referred to interchangeably as Evolved Node B (eNB), E-UTRAN, and Node B) 110, a Mobility Management Entity (MME) 120, and a Serving Gateway (SGW) 130. The User Equipment (UE) 100 connects to an external network via the eNB, the SGW, and a PDN-Gateway (PGW).
The eNB 110 is a Radio Access Network (RAN) node and corresponds to the BSC of the UTRAN system and the BSC of the GERAN system. The eNB 110 is connected with the UE 100 through a radio channel and performs operations similar to those of the legacy RNC/BSC. The eNB may use a plurality of cells simultaneously.
In LTE, all of the user traffics including real time service such as Voice over Internet Protocol (VoIP) are provided through a shared channel, and thus there is a need of an entity responsible for collecting status information of the UEs and scheduling based thereon such as eNB.
The MME 120 is responsible for various control functions, and a plurality of eNBs may connect to one MME.
The SGW 130 is an entity for providing data bearer which is established or released under the control of the MME 120.
The Application Function (AF) 140 is an entity for exchanging application information with the user at the application level.
The Policy Charging and Rules Function (PCRF) is an entity for controlling policy related to Quality of Service (QoS) of the user and transfers Policy and Charging Control (PCC) rule corresponding to the policy to the PGW 160. The PCRF 150 is an entity of controlling the QoS and billing for traffic. Meanwhile, the term “UP” denotes the paths connecting between the UE 100 and the RAN node 110, between the RAN node and the SGW 130, and the SGW 130 and the PGW 160 for data transmission. Among them, the path between the UE 100 and the RAN node 110 is a radio channel which is most resource-restrictive.
In the radio communication system such as LTE, QoS is applied per Evolved Packet System (EPS) bearer. An EPS bearer is used to transmit the IP flows requiring the same QoS. The EPS bearer may be designated parameters related to QoS such as QoS Class Identifier (QCI) and Allocation and Retention Priority (ARP). The QCI is a parameter defined as an integer indicating QoS priority, and the ARP is a parameter for use in determining whether to accept or reject new EPS bearer establishment.
The EPS bearer corresponds to the Packet Data Protocol (PDP) context of the General Packet Radio Service (GPRS). An EPS bearer belongs to a PDN connection which has the Access Point Name) as an attribute. In the case that a PDN connection for IP multimedia Subsystem (IMS) service such as Voice over LTE (VoLTE), the corresponding PDN connection is established using the well-known IMS APN.
In order to support voice telephony in the LTE network, it is possible to use the Packet Switched (PS) mode IMS-based VoLTE or the CS Fall Back (CSFB) reusing the Circuit Switched (CS) mode of the 2nd Generation/3rd Generation (2G/3G) system. VoLTE is the term which can be used in the same concept as Voice over IMS (VoIMS). The terms “VoLTE” and “IMS voice” are used interchangeably hereinafter.
In the case that the UE is in the idle mode, if downlink data or a mobile terminating call addressed to the UE occurs, a paging message is transmitted to notify the UE of the presence of data (or call setup) to receive. Since the paging resource available in one cell is limited, paging messages for plural UEs are crowded, it may occur to transmit the paging messages for part of the UEs due to the restricted paging resource. The voice telephony is a service very sensitive to delay and thus, if the paging signal transmission delay or drop occurs due to the paging channel congestion, the sensible service quality degrades significantly.
Meanwhile, various applications are emerged with the widespread use of smart phones and, in the LTE system supporting only packet networks, the smartphone applications are all classified into packet data applications along with the VoLTE and RCT provided by the operator. There is therefore a need of a method for barring the applications discriminately in the network overload state.
However, since the barring service is activated according to the user's registration as described above, there is a need of defining the UE context to be maintained in HSS, TAS, or SCSCF in order for the operator to bar a certain service arbitrarily. Also, there is no method for notifying the UE of the UE-initiated session failure caused by the Operator Determined Barring.